Best rear end ratio

I would only go lower if you were going to be hooked to a pup full time at 115,000lbs plus.

 

I had a C-15, 18, 3.90, and 11x24.5 in a WS tractor pulling a log trailer with a loader in the center. We are permitted for 110,000lbs here. You won't have a problem, in MY opinion. Good luck

 

But,,,,, if that's what you want, that's all that matters.

 

Little worse fuel mileage, little better torque at the wheels. It's not a huge jump. If you do it then don't forget to have them reprogram the cpc with the new diff ratio so your speedometer will still be correct.

 

I don't think it will be to high geared . Especially if your not pulling a pup trailer.
You have an 18 speed also. They have a very low , low. Shouldn't have any problems.

 

I had a Century with a Mercedes 450 hp 1550 torque 18 spd 4.11 11R22.5 and pulled super b-train. We loaded in farm yards and fields. It always either launched or just spun the wheels being stuck, it never stalled or broke anything. You're probably fine

 

We pull double bellydump trailers with 4.11 rears and it does just fine at 130 k.